Such LED illumination modules are for example used in flashlights. The flashlights known according to the state of art are provided with a light bulb and have a light head generally conically expanding toward the front surface, at the inside of which a mostly parabolically curved mirror is arranged in the focal point of which the light bulb or its spiral-wound filament is arranged. With this arrangement, an optimal light yield is ensured. Disadvantageously, such curved mirrors are easily contaminated or the mirror surface might pale due to corrosion effects so that light reflection is reduced.
In recent times, flashlights provided with a light-emitting diode have come on the market. Light-emitting diodes consume significantly less power than light bulbs and can mostly be operated at a lower operating voltage so that small battery bodies (mignon cells) are sufficient power sources. In particular, flashlights can be produced in smaller dimensions thanks to the application of light-emitting diodes, so that they can be comfortably carried as key fobs or the like. Thanks to their structure, light-emitting diodes are also particularly insensitive to shocks and jarring in addition to the low power consumption. In addition, light-emitting diodes have an extremely long life, so that the light bulb no longer has to be changed very frequently, as was the case in former times. But even when light-emitting diodes are used as light source, the given light emission needs to be optimally utilized. In principle, a reflector can be used, as is the case in some lamps, but this use brings about the already mentioned disadvantages. Moreover, it is desirable that no such component has to be integrated.
In some flashlights known according to the state of the art, a converging lens is arranged at the light output region, which allows for the emission of an essentially parallel light beam in a position in which the point of the light emissions is on the focal point of the converging lens. In one embodiment a lamp head that can be moved along the longitudinal axis has been proposed, allowing for a variation of the position of the converging lens relative to the LED. Thus, the characteristic of the light beam can be changed to some extent. The design, however, can only be used for light-emitting diodes whose radiation is already focused to the front. If the light-emitting diodes also emit relevant parts of light toward the sides, that is under high angle to their axis, the light is not used. Today's high-performance light-emitting diodes sometimes are realized in such manner that the radiation exits under a large angle relative to the axis. The use of adapter lenses is recommended for such light-emitting diodes.
According to the state of the art, prismatically or ray-like massive lens bodies with a planar or slightly convex front face are known. At the rear face the lens bodies are provided with a recess into which the LED glass body projects. In this context, the annular surface of the LED base does not abut the corresponding annular surface of the lens body in a planar way, the light emission point of the LED being stationary such that the light emitted near the optical axis toward the aperture is refracted by the collimator effect such that a parallel light pencil is formed. The light emitted under a larger angle relative to the optical axis is completely reflected once the so-called critical angle is exceeded and deflected according to the surface curvature as well as according to the reflection angle resulting therefrom. In the case of such an adapter lens, known for example from U.S. Pat. No. 6,478,453 or U.S. Pat. No. 6,547,423, the emitting characteristic of the lamp is fixed.